Locomotor activity in the presence of demonstrator mice

We increased the amount of activity in the demonstrator mice to evaluate whether the observer’s activity was mainly provoked by the demonstrator’s activity. We examined whether the observer mice exhibited differences in locomotor activity when observing mice treated with or without MK-801. The cagemate demonstrator and observer mice were individually placed in the appropriate chambers, which were partitioned by a transparent divider. The demonstrator mouse was placed in the centre of one chamber, which was a square surface surrounded by high walls (10 cm × 60 cm × 40 cm). The observer mouse was placed in the centre of the other chamber, which was also a square surface surrounded by high walls (20 cm × 60 cm × 40 cm, Fig. 3a). During the test, the total distance travelled (m) was recorded. We first analysed the behaviour of an observer mouse (n = 8) in the absence of a demonstrator mouse, following which we analysed the observer’s behaviour in the presence of a demonstrator mouse. We then analysed the observer’s behaviour (n = 7) in the presence of a demonstrator mouse injected with MK-801 30 min before testing. The test chamber was illuminated at 100 lx. Data were collected over a 5-min period. Data were analysed using ANY-MAZE software.